There exist positioning procedures which are based on different kinds of technology. On the one hand, there are global navigation satellite systems (GNSS) for positioning. These are generally characterized by having beacons, mostly satellites, which transmit signals to receiving devices which may then calculate their position from these signals by use of the appropriate algorithms. Examples of GNSS include the Global Positioning System (GPS) as well as Galileo. On the other hand, there are terrestrial positioning systems using beacons which are in general stationary and on the surface of the earth. An example for such a positioning capability would be the use of base stations of a cellular mobile communication system for positioning, for instance the use of base stations of a global system for mobile communications (GSM) infrastructure for GSM localization. GSM base stations are used by the appropriate mobile phones for wireless communication. Increasing miniaturization also makes GNSS technology available to this kind of compact devices with a limited energy supply, thus combining the ability to receive both GNSS and terrestrial signals.
Consequently, an increasing number of such devices are configured to use both kinds of signals for positioning.
In this situation, a device may, on the one hand, make a first position determination based on one kind of signal, for example a GNSS based positioning, and also make a second position determination based on a second kind of signal, for example a GSM localization based positioning. The result of each positioning may then be combined in a suitable way, for example by calculating a weighted mean of the two determined positions or by choosing one of the determined positions by a plausibility check.
As an alternative, one positioning capability can be augmented by the use of another communication system that the device is also configured to use. As in the previous example, a device may be configured for GNSS positioning and also GSM communication. The device may then use the GSM communication for transferring information that increases the effectiveness of the GNSS positioning without necessarily making a positioning based on GSM localization. For example, an estimate of the current position may be transmitted to the device from a GSM base station, thus reducing the time for determining a position using GNSS. One specific way of using the capabilities from one system to complement positioning information from another system would be the assisted global navigation satellite system (A-GNSS) in which data from an assistance server may be transmitted to a mobile device, for example by a GSM connection, to improve positioning using GNSS. For the case that the GNSS is GPS, this technique is known as assisted global positioning system (A-GPS).
Mobile devices are not only increasingly endowed with GNSS positioning capability, but also with wireless communication capabilities either for personal area networks, like for example Bluetooth® and ZigBee, or for wireless local area networks, like Wi-Fi and the particular wireless local area network known as WLAN. In particular for the latter kind of network, there are more and more locations, particularly in urban and suburban areas, where an access point (AP) or a plurality of APs are provided by local municipalities, corporations, restaurants or public institutions for general use. These APs are stationary and their locations are sometimes known, so that based on this information positioning as well as navigation is also possible given that the positions are known. The positioning may for example be performed based on a weighted average of the known wireless AP positions based on relative signal strength values. Thus a mobile device may employ a positioning service in different modes, where each positioning mode corresponds to a different kind of signal received based on which a position is calculated.